This invention relates generally to ink jet arrays including a plurality of ink jet channels where each channel includes a chamber, an inlet to the chamber, an orifice from the chamber, and transducer means coupled to the chamber for ejecting droplets of ink from the chamber as a function of the state of energization of the transducer. More specifically, this invention relates to a method of constructing a multi-layer transducer array for a densely packed multi-channel impulse ink jet apparatus.
In liquid droplet ejecting systems of the drop-on demand type, i.e., impulse ink jet printers, a piezoceramic transducer is used to cause expulsion of ink as droplets from a small nozzle or jet. An array of such jets is often utilized in high-speed, high-resolution printers where, as is well known, the printing rate and printing image resolution is dependent upon the number of jets and spacing therebetween. In general, the closer the jets are to one another, the faster the images can be produced and the higher the resulting image resolution.
In typical prior art impulse ink jet printers, printing speed is usually low and only a few jets are provided in a print head. Therefore, highly integrated heads made by combining a plurality of nozzles have been proposed and some of these devices have been put into practical application. However, the conventional ink jet head as taught by U.S. Pat. No. 4,364,067 Koto et al can include approximately seven to seventeen nozzles at best. Print quality suffers, and as a result there has been no printer of this type having printing characteristics which are comparable to the quality produced by using a solid front. Also, the integrated ink jet heads of the prior art tend to be large in size and complicated in construction.
Accordingly, layered or laminated ink jet structures have been utilized to facilitate fabrication of ink jets which necessarily require a high degree of precision. Even higher degrees of precision are required in densely packed multi-channel impulse ink jet arrays. However, there are certain limitations on high density. The most important limitation involves cross talk between channels. Of course, cross talk is undesirable and it is, therefore, necessary to provide a certain structural spacing between channels. This is sometimes achieved by using a fan-in technique such as that disclosed in U.S. Pat. No. 3,988,745--Sultan.
As also shown in Sultan, the ink jet chambers and transducers associated therewith are staggered with respect to one another. There are, however, limitations as to the amount of fanning-in which may be done and this necessarily imposes limitations on the number of channels which may be utilized in such an array. Moreover, when attempts are made to add channels by adding layers to the device, the spacing or resolution of the channels within the device is increased, i.e., the clarity is reduced.
One solution that has been proposed is taught in U.S. Pat. No. 4,392,945--Parkola, which is assigned to the assignee of the present invention and incorporated herein by reference. Parkola shows a multi-layer ink jet apparatus which includes a plurality of channels comprising chambers including inlets and orifices and transducers coupled to the chambers. The various channels are located in different layers that stagger with respect to a plane traverse to the layers so as to achieve a high density array of ink jet orifices. In such a manner, the apparatus provides a high degree of precision which is required in densely packed multi channel impulse ink jet arrays. The Parkola device, however, is of the edge-exit type which necessitates the use of either screws to maintain the entire laminated structure as a unit or an epoxy to form a bond between the laminations. It is, therefore, desirable to provide a densely packed transducer array which is not of the edge-exit type. Such an array is disclosed in the ink jet printer of U.S. Pat. No. 4,459,601--Howkins, which is assigned to the assignee of the present invention and incorporated herein by reference.